Method and apparatus for hydraulically classifying coal of very small sizes



Nov. 16, 1954 E. HARVENGT 2,694,490

METHOD AND APPARATUS FOR HYDRAULICALLY CLASSIFYING COAL OF VERY SMALL SIZES "116d Nov 7, 1950 l0 Sheets-Sheet l gill INVENTOR 'ldmzzdlalwezyi YP MW .rrl iriu! ATTORNEY NOV. 16, 1954 E, V G 2,694,490

METHOD AND APPARATUS FOR HYDRAULICALLY CLASSIFYING COAL OF VERY SMALL SIZES lled NOV. 7, 1950 l0 Sheets-Sheet 2 ldmMd/Yarvezyl' WW ATTORNEY Nov. 16, 1954 E. HARVENGT METHOD AND APPARATUS FOR HYDRAULICALLY CLASSIFYING COAL OF VERY SMALL SIZES l0 Sheets-Sheet 3 iled Nov. 7, 1950 INVETOR Idmmd/Yarvezyf BYII/ZI ATTORNEY N 1 1954 E. HARVENGT METHOD AND APPARATUS FOR HYDRAULICALLY CLASSIFYING COAL OF VERY SMALL SIZES l0 Shets-Sheet 4 iled Nov. 7, 1950 INVENT OR Edmazzdlarvezgl Bum/Q W ATTORNEY NOV. 16, 1954 E HARVENGT 2,694,490

METHOD AND APPARATUS FOR HYDRAULICALLY CLASSIFYING COAL OF VERY SMALL SIZES 119d NOV. 7, 1950 '10 Sheets$heet 5 q INVENTOR ATTORNEY 2,694,490 ARATUS FOR HYDRAULICALLY l0 Sheets-Sheet 6 Y INVENTOR ATTORNEY Immfl arveryi E. HARVENGT HOD AND APP CLASSIFYING COAL OF VERY SMALL SIZES MET IHH m N llum Nov. 16, I 954 iled NOV. 7, 1950 Nov. 16, 1954 A E. HARVENGT METHOD AND APPARATUS FOR HYDRAULICALLY CLASSIFYING COAL OF VERY SMALL SIZES Filed NOV. 7, 1950 l0 Sheets-Sheet 7 INVENTOR ldmmdflmenyi BY & H I

%' AfiORNEY' Nov. 16, 1954 E. HARVENGT METHOD AND APPARATUS FOR HYDRAULICALLY CLASSIFYING COAL OF VERY SMALL SIZES l0 SheetsSheet 8 iled Nov. 7, 1950 INVENTOR Nov. 16, 1954 E. HARVENGT METHOD AND APPARATUS FOR HYDRAULICALLY CLASSIFYING COAL OF' VERY SMALL SIZES l0 Sheets-Sheet 9 iled NOV. 7, 1950 ATTORNEY.

N v 16, 1954 E. HARVENGT METHOD AND APPARATUS FOR HYDRAULICALLY CLASSIFYING COAL OF VERY SMALL SIZES l0 Sheets-Sheet 10 iled Nov. 7, 1950 lN vENToR fldmazzd/Yarvezyf BY 2 m heavy particles.

METHOD AND APPARATUS FOR HYDRAULI- CALLY CLASIFYING COAL F VERY SMALL SIZES Edmond Harveugt, Moustier-sur-Sambre, Belgium, assignor to Link-Belt Company, Chicago, 111., a corporation of Illinois Application November 7, 1950, Serial No. 194,449

12 Claims. (Cl. 209-18) The invention relates to the treatment of coals of very small sizes, and particularly concerns the treatment of such coals which are not, or are imperfectly, dustfreed only when they contain considerable quantities of fine A known economical method of treatment of such coals comprises subjecting the same to a dry :dust freeing operation wherein, in order to separate most of the 'fine heavy particles, the major portion of the fine particles is extracted from the coals, and the remainder is subjected to a complementary, preferably wet, treatment in order -to separate out the remaining'heavy particles and to divide the other particles into categories of products.

The present tendency in mining results in coals having a substantial moisture content such that the dry dust freeing operation cannot longer be directly applied or will lose its efficiency to such an extent that the subsequent treatment leads to commercially nonusable products.

The problem is thus to treat directly, and in a simple and economical manner, the coals of very small sizes in a more or less wet state, and usually in considerable quantities, having regard to the fact that in the usual washing processes in troughs, fine heavy particles are found in substantially all of the portions of the washing bed and cannot be removed therefrom except with difliculty.

The purpose of the invention is mainly to resolve the aforesaid problem.

According to the invention, the coals of very small sizes which are not, or are imperfectly, freed from dust. which have a high content in fine heavy particles, and which additionally may be comparatively Wet, are subjected in troughs provided with a liquid current first to a grading by density and thereafter to the action of liquid pulses without noticeable suction effect, together .with a removal of the fine heavy particles which have reached the bottom of the bed, so that the bed remaining after this removal may be divided into its various categories of products.

In accordance with another feature of the invention, especially when considerable quantities of materials are to be treated and/or the content in fineheavy particles of these materials is comparativelyhigh, subsequent to the grading by density and the removal of the fine heavy particles which have reached the bottom of the bed as specified above, there isseparated from the residual bed a fraction thereof comprising the lowercornponent layers.

This fraction is carried away or preferably subjected again to a grading by density followed by the removal offineheavy particles as hereabove outlined. The upper remaininglayers of the said residual bed are divided into categories, or subjected to a grading operation that is followedby the removal of fine heavy particles. The ultimate residual bed is finally divided into categories of products.

In accordance with an alternate to .the above outlined method, followingthe first grading by densityand "the first removal of heavy fineparticles, there are separated in succession fromthe residual bed several.frac- 'tions of the said bed, each beingformed of thelower component layers, and each suchfractionjis subjected .to a grading by density followed by the removal of fine 7 'heavyparticles. The residual beds of these various'treatments are then divided intocate gories of products.

I'In each ,ofthe above cases, the iddlingsmaybe rewashedif desired and to accomplishthi's, theyarereintroduced into the process, preferably by being reyturne'd:togtheheadthereof.

For carrying the invention into practice use is made of plants comprising washing troughs, and jigs working in direct combination, with the jigs being provided with means for balancing entirely or to any desired extent the ;suction eflect therein order .to enable the fine heavy particles to percolate through the bed to the lower portion thereof, as well as extracting'apparatus operating at full level and adapted to separate fractions formed of the lower ;layers of the bed without notice,- able disturbance of the said bed.

In order that the invention may be well understood, certain preferred embodiments thereof will now be described jointly with certain plants adapted for carrying the invention into practice, which plants are illustrated, by way of example only, in the accompanying drawings, in which:

Figure 1 is a side elevational view of one plant em- Figure 6 is -a side elevational view of a furthermodified form of'plant embodying the invention,

Figures 6a and 6b collectively provide a longitudinal,

vertical sectional view, on an enlarged scale, ofthe plant of Fig. 6.

Figure 7 is a side elevational view of a still further modified form of-plant embodying the invention,

Figures 7a and 7b collectively provide a longitudinal, vertical sectional view, on an enlarged scale, of the plant of Fig. 7,

Figure 8 is a side elevational view of another modified form of plant embodying the invention, and

Figures 8a and,8b collectivelyprovide a longitudinal, vertical sectional view, on an enlarged scale, vof the plant of Fig. 8.

Referring to thedrawings, and first to Figs. .1 ,to 4, .1 designates a washing, or alluviation trough, of appropriate slope and provided with a liquid current, and

2a designates the bin of the jg 2, provided with a sieve 4 and liquid impulses, for example, generated-by apiston -5 reciprocatedlby means ofan eccentric gear6-rnounted ,on a rotating shaft 7 actuated by a power system not illustrated.

Means are provided for balancing to any desired extent the suction eifect resulting from the nonworking strokes of the piston 5, fo r example, a rotary valve liquid feeding mechanism 8=actuated.by the drive for the piston -5, thearrangementbeing such that theliquid from a pipe 811 is introduced into the chamber 8b abovethe. piston 5 during theworkingor descending strokes of said piston,

and forced into the bin Zwbelowthepiston 5 during the apparatus is preferred, other balancing arrangements could be adopted.

At the outlet end-10 of the sieve 4- there is provided an adjustable weirltlaand above the sieve is arranged a cross partition '11 having an external extension 12 arranged as an overhanging-shelf. Associated with the partition 1 1is a slidevalve 11a provided with :a device for adjusting the depth'thereof, for example a screw drivegenerally indicated-11b; With the outlet end'10 is preferably c'ombineda full'leveloperated'extractor-9 including a chamber 12aprovided to- "ivardsthe lend thereof, with abala'nced'shutter 13 so arranged that'the1Qchambe1-"l2a is 'riormally closed and is opened' only lv'vhen the shutter yieldsunder the pressure of i hl aattt l nahar iie n a tt "T v e shutter provides an open "s1ot'fo"r' the-material's between its 2,694,490 Patented Nov. 16, 1954 own edge and the wall 14 of the chamber 12a, said slot being automatically closed when the pressure of the materials on the shutter decreases.

An adjustable liquid supply adapted to form an ascending current through the discharge slot may be provided as at 12c.

Continuous discharge means arranged at the bottom of the extractor 9 comprises a drum 15 having pockets 16 and mounted on a shaft 17 rotating within a casing 18 provided with a discharge opening 19, the shaft 17 being moved by a suitable drive, not shown.

The materials discharged from the chamber 12a are received within the pockets 16 of the drum 15 and in turn are discharged through the opening 19 as the drum rotates.

On the other hand, in the lower part of the bin 2a is arranged a discharge device, preferably operating in a continuous manner, and which may be formed with advantage of a rotating drum 15a having pockets 16a and mounted on a shaft 17a rotated in any convenient manner as by means of a transmission gear 17b from the driven shaft 17 of the drum 15.

The described arrangements are not limitative and apparatus of difierent kinds could be used provided they operate at full level, that is without causing substantial disturbance of the bed in the trough.

Following the jig 2 and extractor 9 there is provided a washing trough section 101, and with this section is preferably associated a jig 102, which is constructed similarly to the described apparatus 2, and an extractor 109 constructed in a manner generally similar to the apparatus 9 already described.

Following the apparatus 102 and 109 there is a trough section 20 and at a suitable location in this section there are arranged one and preferably two extractors 21 working at full level and which, with advantage, are of the pocket type.

Such an extracting apparatus comprises, as illustrated in part in Fig. 3, a hopper 21a in communication with the trough through a transverse slot 21b, this slot being provided with two movable and adjustable shutters of which the one 210 is provided with a nose 21d forming a protrusion above the bottom of the trough while the other 21e is adapted to move in the plane of the slot in order to increase or decrease the width thereof. Within the hopper 21a is arranged an adjustable liquid supply producing through the slot 21b an adjustable ascending current in the direction of the trough. At the bottom of the hopper is connected an evacuating apparatus comprising a drum 21 having pockets 21g and mounted on the shaft 2111 supported for rotation in a casing 21i surrounding the drum and provided with a discharge opening 21 The shaft 2111 is actuated at a suitable speed by means of a drive, not shown, so as to evacuate through the discharge 21j the materials passing through the adjusted slot 21b and filling the pockets 21g. Moreover, following the extractor or extractors 21, there is mounted in the trough section 20 one or two extractors or evacuating apparatus 22 working at full level and which may be extractors of the pocket type such as the extractors 21, but which, owing to the usually reduced quantities of materials yet to be evacuated at this stage of the treatment, may be evacuators of the flap type, preferably as described in the Belgian Patent No. 455,896, dated May 26, 1944. One embodiment of such an apparatus is illustrated in Fig. 4 and comprises a hopper 22a communicating with the trough through a transverse slot 21b provided with two movable and adjustable shutters 21c and 21e, the hopper being provided with an adjustable liquid supply forming an adjustable ascending current through the slot. The hopper is extended downwardly by a chamber 22b preferably of conical or pyramidal shape provided with a lower opening 220 the size of which is in any case sufficient to enable the unrestricted passage therethrough of the largest particles to be evacuated, while it is provided at its bottom end with a supporting member or plate 22d which may be perforated and which is adjustable relative to the opening.

If desired, at the end of the trough section 20 may be mounted a sloping sieve 23 equipped with spraying means 24 and adapted to receive the discharge of the trough.

Finally, known means indicated at 25 may be provided for periodically returning, particular to the head of the trough section 1, the products collected at the discharges of the extractors 22.

In a plant arranged as just described, the treatment of the wet small sized coals not, or imperfectly only, freed from dust and of high content in fine heavy particles, is performed as follows.

The coals supplied at the head of the trough section 1 grade themselves by density therein, the fine heavy particles tending to reach the bottom of the bed together with the heavy coarse or schist particles, and the thus graded bed reaches the first group of jig and extracting apparatus 2 and 9, respectively. The mesh size of the sieve 4 is chosen to enable the fine heavy particles to pass therethrough. Owing to the liquid impulses with no suction effect that are communicated to the materials on the sieve, the washing bed is opened up without being materially disturbed, thus permitting the fine heavy particles already occupying the bottom of the bed to pass through the sieve while those yet retained in the higher layers of the bed may be accelerated in their descending movement so as to finally reach the sieve and pass therethrough. These fine heavy particles are connected in the bin 2a and are discharged by the pocketed drum 15a. The heavy coarse or schist particles are retained on the sieve and pass at the outlet end thereof into the chamber 12a where they accumulate until the quantity thereof is sufiicient to cause the yielding of the shutter 13. The heavy coarse particles then pass into the pockets of the drum 15 which carry them towards the discharge 19.

The remainder of the bed passes over the weir formed by the partition 11 and the adjusted sliding valve 11a and reaches the section of the alluviation trough 101 where a regrading takes place with passage of the residual heavy particles as well as the residual heavy coarse particles to the bottom of the bed. When this regraded bed reaches the jig 102 and the extractor 109, the heavy fine particles are eliminated through the sieve 104 and the pocketed drum of the apparatus 102, and the coarse particles retained on the sieve are evacuated by the pocketed drum of the apparatus 109 in accordance with the process above outlined.

The bed of materials that reaches the trough section 20 contains substantially no heavy fine particles. It can then be divided into categories of products, with the small quantity of schists yet contained therein being caught and eliminated at the extractor or extractors 21 together with such portion of the mixed schists that it may be desirable to eliminate. The middlings are collected at the extractor or extractors 22 and the clean coals are collected either at the end of the section 20 or at the end of the sloping sieve 23 after being subjected to a sprinkling operation which is intended to free the clean coals of any adhering minute particles, such as argillaceous particles.

According to the intended use for the middlings they are collected at the extractor or extractors 22, or are cyclically returned to the process, as along the path 25, to the head of the trough section 1.

Experiments have shown that while treating a raw coal 0-6 mm. not freed from dust and showing an ash content of 38.88%, while containing 38.4% of particles smaller than 1 mm., with sieves of 2 mm. mesh size, subsequently to the elimination of the fine heavy particles, coals are obtained showing 12.58% of ash content while the products discharged at the apparatus 2 and 102 showed 82.40% and 74.50% of ash content respectively, and the products discharged at the apparatus 9 and 109 showed 76.05 and 79.50% of ash content, respectively.

The exemplative plant described with reference to Figs. 1 to 4 is related with applications wherein, owing to the composition of the starting materials, and after removal of the fine heavy particles, it may be desirable to divide the residual bed into various categories of products. One such case, for example, will be that of the treatment of a raw coal. However, the division of the residual bed will not always be necessary and in certain cases, as when the starting materials are formed of a mixture of fine particles, it may be sufiicient to eliminate the fine heavy particles from said starting materials to form therewith a valuable or at least saleable product.

Figs. 5, 5a and 5b show a plant which may be used for this purpose. In this plant may be found the trough 1 and the jig 2 and extractor 9, as well as the trough section 101 and the jig 102 and extractor 109 of Fig. 1,' the discharges of the apparatus 2, 9, and 102, 109 being considered as true schists. The materials remaining in the trough beyond the extractor 109 may form the final for the extraction of the values therein. separation a double result'is immediately secured, 1. e.:

pre ame cleaned or improvedproduct, but to secureaa moi-emere fect cleaning-or amateriallytenhanced improvementsof .this product, theapparatusltwis followed by a trough section .ltllA in which is ars'angedta jigl-02A .andan extractor ltwAboth similar totheapparatusgZand 9, or 162 and M9 respectively. Then according to whether the starting materials do. or do notinclude, a large proportion of fine heavy particles, the dischargeofthe jig 1102A will contain only a small proportion of thesefine ;heavy particles together with .middlings from which ;it imaybe desirable to extract the values, or suchaproportion of fine heavy particles that it must be considered as a residue. Inthe; former case said discharge is subjected ;to a so called rewashing, for example byreturningsame to the head of the trough 1. as indicatedaat 25A; while :in the second casesaiddischarge is mixed with those of .the apparatus 2 and 9,.and ltlzandltlithat is with the true schists.

In both cases, the discharge of the-apparatus 109A willusually form a product havinga substantial .proportionof valuable particles which is preferablyprewashed, for example by returning it to the head of the trough l as indicated at 25A. The cleaned and improved product is collected at the end; of the, section 20 of the washing trough.

When for a given trough section the:quantities to be treated increase, the depth ofthe bed increases andthe fine heavy particles contained in the central and upper layers of the washing bed normally tend to-rernain therein. Owing to the pulsations without suction etfect imparted to the bed while it is passed over the sieves of the jigs such as 2 and 102, the composition of these central and upper layers is very materiallyimprovedat the-expense of that of the lower layers, without -however,'all of the fine-heavy particles having reached the bottom of the bed so that they should be eliminated-while the materials pass over the aforesaid sieves.

In such a case,in accordance with the 1nvent1on, a more or less considerable part of -the lower portion of the bed is then separated, the separated'fraction being,

as the case may be, considered as a residue or retreated Owing" to this first, of considerablyreducing the volume of the bed containing the valuable products so that its subsequent cleaning treatment and its separation into categories of products is greatly facilitated and, second, to enable the fine heavy particles yet contained in the central'and'upper layers of the bed to befreed therefrom in an easier manner and toreach the bottom of the bed in order to be eliminated.

Figs. 6, 6a and 612 show a plant generally similar to that of Fig. l, but completed so asto enable the process just described to be performed. Inthis figure, and within the section 20 of the washing trough, and following the two extractors 21 and a regrading section trough 20A, there is arranged a jig 2-02 and an extractor-209 similar to the apparatus-2 and 9, or 102 and 109,-respectively, of the plant illustrated in Fig.1. At the said extractors 21, following a first se aration of the fine-heavy particles and coarse schists at the apparatusZ and 9. and 102and 199, there is separated from the residual bed; as'a residue,

2. fr cti n f rmed substantia y by he major orti n of the residual tai ings. 'The depth of the-remaining bed thus is materially reduced. with the-central and upper'layers correspondingly positioned nearer the bottom of the trough. When the materials pass over the sieveof the ji 2&2, the liquid impulses without ap reciable suction effect to which the remaining bed is sub ected have the result of permitting the fine heavy particles which have reached the bottom of the bed, and the major portion of .those yet contained in the said central'and upper layers,

and 24, respectively, of Fig. 1, not illustrated. According to the illustration. the two extractors, such as 21, which are located in the end portion of the'troughsection 2 3A f rnish a product to be rewashed and a -furth er extractor .22 furnishes a usable ,middling product.

5 to;answer this requirement.

.theddischargesifmm: the extractors-' .2.1.: :.th rough secvtion120A.will be :retreated ,for. the extraction therefrom Of the valuableywproducts yet contained; therein.

In; principle:the;-plant of Figs. 7,' 7a; and 7b ;is intended In these figures, the discharges frorn -the extractors -21; and; from one or several -,apparatus;such:as 22 of Fig. 1,-are retreated in a trough ,26cquipped with. a jig 302 and ,a conjugated extractor 399 as wellas, for example, anextractor 3210f the 10 'pocket. type, andgan extractor 322 of the flap valvetype,

,similar to the apparatus '21 and '22,,respectiv ly, of Fig. land as hereinbefore described.

In.fact,, following a first separation of-fine heavy and coarse schist particles effected; at the apparatus Zand 9,

11:5 -and1102 and'gltl9, there isseparateda portionof the bed comprising the lower layers and a;fractiony.of thacentral layers, the portion thus separated being regarded in the; head section of the.,trough;26 in ordento be freed Qfromthe fine-heavy andzcoarse schist particlcsthereinat P :theapparatusfitlZ and .309. ,The; remainder of the bedis subjected ,to a, final; cleaning and separation in the, down- .stream .section; of the trough -,26. .and at .the apparatus; 321 8.1}(1322.

, 'I,he:following categories .ofproducts are'collectedfrom ;the ;plant'ot Fig.7. .Cleangcoala -which. maypor. may not "be caused I0.:P?1SS ;over a sloping sievewi-th sprinkling gmeansyat the end ofpthe troughsection'JZt). :At the ap- .1para.tus.';22;of;this:tr0ugh section 29, and at. the .end of .the trough-26, .aproduct which may be usedqas a middling .30 rtproduct but which. may be..also cyclically returned to the process, such. as along the path =25. to the; head of .the .trough-section 1. Fineheavyandcoarse schist; particles may be eliminated at: the discharges. of the: apparatus :2 3311619, 1tl2;and;109,aand 3tl2qandz3il9. 'At thenextractor '35 322 a more or less schistous product. which is conveniently rreturned in. cycle to the process such as-along 27 to the :headof the trough :26. Finally, at the discharge of the apparatus 321 aproduct near :theipure schists which may be eliminated either together with the schists or united 401withthe product to: be rewashed which is collectedat the discharge .of the1apparatus'322.

Finally, where the quantities on materials tobe treated are considerableorwhen the. content. in fine heavy particlesof these materials is particularlyhigh, the plant may .145 "be arranged as illustrated in-Figs.z8, 8a and 8b in accor'dance to which, followinga first removal of heavy fine and :coarse schistparticlealithere is effected several successive separations of the lower'portions of the residual bed, each raction. thus separated being preferably subjected to a complementary treatment including the removal of fine heavy particles.

I In. these figuresmay be found again the trough sections :1, 101 and-20 with the same equipment inFig. 1; together with the additional trough section 101A equipped with 55. apparatus 102A and 1439A. The extractorsi 21 'and'22 of the trough section 20, however, are three: in number in .each. case. The;sieve':23 with its liquid sprinkling means 24 is associated with thegeneral coal discharge.

:The extractorsZl are arranged and adjusted to separate :from the bed, downstream of the apparatus 102A and 1109A, a part'of the lower portion of the bed. "The discharge of the. apparatuszl is carried to the head of a trough23 equipped with the apparatus 4'92 and 409, similar tothe apparatus Z and 9, or 102 and 109, as well as 6 -with two extractors :421 of'the pocket type similar to the extractors 21 alreadydescribed.

'Withthis arrangement there is eliminated from the bed the line heavy particles at the apparatus 402 and the coarse schist particles at the apparatus 409. The dis- 7 -charge of the apparatus 421 isforrned of a product of high content in schists which should be eliminated with the residues. At the end of the trough is collected a prod- :uct which-in mostcases is to berewashed and for this .c-reason is returned toithe head'of the'trough section'l 7 5 along the-path-Gll.

At the'apparatus-of :the trough sectionZd, there is ex- .tracted; from theresiduaLbedanother portion of its lower layers,..which-portien is carriedz to'the head of a trough .i29-which'is preferably equipped asillustratedwith a single jig '502' followed: with one; or; two extractors 522 similar to the apparatus; 22 already described.

=Iheapparatus :;502,eliminat es from the formed bed .the fine heavy particles that may be present in-the' frac- 110,113 extractedzbyg the; apparatus22 of the troughirscction It is to be,understood .-that when -nece,ssary-,or desirahle,;?- 20, while the extractor or extractors 522 separate-from the bed a mixed product which may be used as such or, as indicated in the figure, may be united with the product collected at the end of the trough 28 to be returned in cycle to the process, for example along the path 30 to the head of the section 1 of the upper trough. At the end of the trough 29 there is collected coals which are to be united to those collected at the end of the section 20 of the upper trough, these coals being preferably washed on a sieve 23 provided with a liquid sprinkler 24.

As will be understood, should the content in fine heavy particles so require, from the residual bed in the trough section 20 there may be separated a third portion of the bed, to which may be applied a treatment similar to that carried out in the trough 29, or this trough section 20 could be equipped with a jig such as 2, in order to eliminate the fine heavy particles therein.

1 claim:

1. A process for treating coals of very small sizes which are not, or are imperfectly, freed from dust and are of high content in fine heavy particles, comprising partially classifying the starting mixture of materials by density into layers by flowing the said materials down an inclined path in a stream of liquid, further classifying the entire partially classified bed, to permit fine heavy particles still remaining in the upper layers to percolate to the bottom of the bed, by moving the said bed bodily over the screen of a jig while retaining the previously effected classification of the bed and flowing surges of additional liquid in an upward direction through said screen and the bed of materials supported thereon while absorbing any downward flow of liquid through the bed of material, removing the percolated fine heavy particles substantially free from light particles through the bottom of the bed while it is passing over the screen, parting the classified bed as it leaves the jig into upper and lower fractions and removing the lower fraction, and after the upper fraction of the bed has moved beyond the jig separating the same into categories of products.

2. The process of claim 1 characterized by further classifying the upper fraction of the parted bed, to deliver to the bottom thereof any remaining heavy particles, by flowing the bed down an inclined path in a stream of liquid, removing from the bottom of the further classified bed a fraction containing said remaining heavy particles, and separating the remaining upper portion of the bed into categories of products.

3. The process of claim 1 characterized by further classifying the upper fraction of the parted bed, to deliver to the bottom thereof any remaining heavy particles by flowing the bed down an inclined path in a stream of liquid, removing from the portion of the further classified bed a fraction containing said remaining heavy particles, separating the remaining upper portion of the bed into middlings and coal, and returning the separated middlings to the starting mixture of materials to be reprocessed therewith.

4. The process of claim 1 characterized by further classifying the upper fraction of the parted bed, to deliver to the bottom thereof any remaining heavy particles, by flowing the bed down an inclined path in a stre m f liouid, removing from the bottom of the further classified bed a fraction containing said remaining heavy particles, separating the remaining upper porti n of the bed into categories of products, further classifving the said removed fraction containing the heavy particles by flowin the material down an inclined ath in a stream of liquid. removing from the bottom of the flowing bed the s id heavy partic es, and separating the remaining bed into categories of products.

5. The process of claim 1 characterized by further classifyin the upper fraction of the parted bed, to deliver to the bottom thereof any remaining heavy particles, by flowing the bed down an inclined path in a stre m of liouid. removing from the bottom of the further classified bed a fraction containing said remaining heavv particles, separating the remaining upper porti n of the bed into categ ries of product. further classifying the said removed fraction containing the heavy particles by flo in the material down an inclined path in a stream of liquid, removing from the bottom of the flowing bed the said heavy particles, separating the remaining bed into categories of products, and returning one of s id last mentioned roducts to the said fraction contai iling the heavy particles for further classification therewit 6. The process of claim 1 characterized by further classifying the upper fraction of the parted bed into layers by flowing the bed down an inclined path in a stream of liquid, successively separating from the bottom of the further classified bed a first fraction containing the remaining heavy particles and a second fraction including middlings so as to leave coal in the flowing stream, separately further classifying the said successively separated fractions by flowing the fractions down individual inclined paths in streams of liquid, removing from the bottom of the flowing bed formed of the said first fraction the heavy particles and returning the remainder of the bed to the original starting mixture of materials to be reprocessed therewith, removing from the bottom of the flowing bed formed of the said second fraction the middlings and returning the same to the original starting mixture of materials to be reprocessed therewith, and mixing the remainder of the bed formed of the second fraction with the aforesaid coal.

7. A plant for treating coals of very small sizes which are not, or are imperfectly, freed from dust and are of high content in fine heavy particles, comprising an inclined washing trough, having a smooth bottom surface, along which the starting mixture of materials flows in a stream of liquid so as to be partially classified by density into layers, a jig directly connected to the lower end of the trough to receive the entire bed of materials from the trough in its partially classified condition, said jig having a screen to support the bed of materials while it moves bodily through the jig and the previously effected partial classification of the bed is retained, and means in the jig for flowing surges of additional liquid in an upward direction through the screen and the bed of materials supported thereon while absorbing any downward flow of liquid through the bed of material to further classify the entire bed by permitting fine heavy particles still remaining in the upper layers to percolate to the bottom of the bed and pass through the jig screen, means at the discharge end of the screen for parting the classified bed leaving the jig into upper and lower fractions, an extractor for removing from the bed the parted lower fraction, and means connected to the extractor to receive the parted upper fraction of the bed and separate the same into different categories of products.

8. A plant as in claim 7 further characterized by an inclined washing trough, having a smooth bottom surface, connected to the extractor to receive the parted upper fraction of the bed for movement therealong by liquid discharged from the jig for further classifying the bed into layers, an additional extractor connected in said last mentioned Washing trough for removing from the bottom portion of the bed the remaining heavy particles, and means connected in the last mentioned washing trough beyond said additional extractor for separating the remaining bed into different categories of products.

9. A plant as in claim 7 further characterized by an inclined washing trough, having a smooth bottom surface, connected to the extractor to receive the parted upper fraction of the bed for movement therealong by liquid discharged from the jig for further classifying the bed into layers, additional extractors connected in said last mentioned washing trough for successively removing from the bottom portion of the bed a first fraction containing the remaining heavy particles and a second fraction including middlings, and means for returning the said second fraction including the middlings to the upper end portion of the first mentioned washing trough for reprocessing with the starting mixture of materials.

10. A plant as in claim 9 further characterized by the provision of an additional inclined washing trough, having a smooth bottom surface, receiving the said first fraction containing the remaining heavy particles for movement therealong in a stream of liquid for further classification into layers, a iig connected in the intermediate portion of the additional trough and having a screen for supporting the entire bed, means in the iig for generating liquid pulses without noticeable suction effect and passing them only in an upward direction through the screen and the bed supported thereon to further classify the bed and to remove the heavy particles that pass through the screen, means connected in the said additional washing trough beyond the jig for extracting additional categories of products from the bottom of the bed, and means for returning the material discharged from the end of the said additional trough to the upper end portion of the initial trough for reprocessing with the starting mixture of materials.

11. A plant as in claim 10 further characterized by means for returning to the upper end of the said additional washing trough one of the said products extracted from the bottom of the bed in said trough.

12. A plant as in claim 7 further characterized by an inclined washing trough, having a smooth bottom surface, connected to the extractor to receive the parted upper fraction of the bed for movement therealong by liquid discharged from the jig for further classifying the bed into layers, additional extractors connected in said last mentioned washing trough for successively removing from the bottom portion of the bed a first fraction containing the remaining heavy particles and a second fraction including middlings, two additional inclined washing troughs for separately receiving the said first fraction containing the remaining heavy particles and the said second fraction including middlings, said additional washing troughs further classifying their respective fractions of the parted bed into layers as the fractions flow therealong in streams of liquid, means connected in each one of the two additional washing troughs for separating their classified beds into different categories 10 of products, and means for combining one product from each one of said additional washing troughs and returning the combined products to the upper end portion of the initial washing trough for reprocessing with the starting mixture of materials.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,100,904 Neill June 23, 1914 1,508,176 France Sept. 9, 1924 1,544,999 Lequeux July 7, 1925 1,696,767 Hoyois Dec. 25, 1928 1,789,516 Crangle Jan. 20, 1931 1,845,602 Hoyois Feb. 16, 1932 1,912,077 Hoyois May 30, 1933 2,104,090 Montgomery Jan. 4, 1938 2,122,039 Logue June 28, 1938 2,194,139 Davis et al Mar. 19, 1940 FOREIGN PATENTS Number Country Date Great Britain Sept. 25, 1924 

